Repurchase Agreements - Narrative (Detail) (USD $)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012
Repurchase Agreements:
Repurchase agreements - outstanding	$ 61,781,001,000	$ 102,785,697,000
Repurchase agreements - weighted average borrowing rates	2.33%	1.53%
Repurchase agreements - weighted average remaining maturities (in days)	204 days	191 days
Repurchase agreements - collateral held, fair value	67,900,000,000	109,200,000,000
Repurchase agreements - accrued interest	$ 222,100,000	$ 363,800,000